CONICET | Buscador de Institutos y Recursos Humanos

S. typhimurium is a Gram-negative pathogen that causes various host-specific diseases. During their life cycle, Salmonellae survive frequent exposures to a variety of environmental stresses, e.g. carbon-source starvation. The virulence of this pathogen relies on its ability to establish a replicative niche, named Salmonella-containing vacuole (SCV), inside host cells. However, the microenvironment of the SCV and the bacterial metabolic pathways required during infection are largely undefined. The objective of this work was analyses the metabolic state of the pathogen in different stages and conditions during infection. For this we developed different biological probes whose expression is modulated by the environment and the physiological state of the bacterium. We constructed transcriptional reporters by fusing promoter regions to the gfpmut3a gene, to monitor the expression profile of genes involved in glucose utilization and lipid catabolism. The induction of these probes by a specific metabolic change was first tested in vitro, and then during different condition of infection in macrophages, using flow citometry analysis. We were able to determine that Entner-Doudoroff is the main metabolic pathway utilized by Salmonella during infections in mouse macrophages. Furthermore, we found sub-populations of bacteria expressing genes involved in pathways for the utilization of different sources of carbon, including beta-oxidation and glycolysis. These populations are modified in presence of different metabolizable substrate and the initial metabolic state of the bacteria, suggesting the coexistence of Salmonella with diverse metabolic states during the infection.

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